EP0589349A2 - Polyamide mouldings for the preparation of articles using blow-moulding, profile-extrusion or tubular extrusion - Google Patents

Abstract

The use of thermoplastic polyamide (nylon) moulding compositions containing A) 40 - 99.7% by weight of a polyamide having a viscosity index of >/= 250 ml/g, B) 0.3 - 3% by weight of an olefin polymer built up from b1) 40 - 99.8% by weight of at least one alpha -olefin having 2 - 8 carbon atoms, b2) 0.2 - 20% by weight of an ethylenically unsaturated mono- or dicarboxylic acid or a functional derivative of such an acid, C) 0 - 50% by weight of fibrous or particulate fillers, or mixtures thereof, D) 0 - 30% by weight of conventional additives and processing auxiliaries, for the production of mouldings by blow moulding, profile extrusion and/or tube extrusion.

Description

• A) 40 - 99,7 Gew.-% eines Polyamids mit einer Viskositätszahl ≧ 250 ml/g
• B) 0,3 - 3 Gew.-% eines Olefinpolymerisates, aufgebaut aus
  • b₁) 40 - 99,8 Gew.-% mindestens eines α-Olefins mit 2 - 8 C-Atomen,
  • b₂) 0,2 - 20 Gew.-% einer ethylenisch ungesättigten Mono- oder Dicarbonsäure oder einem funktionellen Derivat einer solchen Säure,
• C) 0 - 50 Gew.-% faser- oder teilchenförmige Füllstoffe oder deren Mischungen
• D) 0 - 30 Gew.-% übliche Zusatzstoffe und Verarbeitungshilfsmittel

zur Herstellung von Formkörpern durch Blasformen, Profilextrusion und/oder Rohrextrusion.The invention relates to the use of thermoplastic polyamide molding compositions containing

• A) 40-99.7% by weight of a polyamide with a viscosity number ≧ 250 ml / g
• B) 0.3-3% by weight of an olefin polymer built up from
  • b₁) 40-99.8% by weight of at least one α-olefin with 2-8 C atoms,
  • b₂) 0.2-20% by weight of an ethylenically unsaturated mono- or dicarboxylic acid or a functional derivative of such an acid,
• C) 0 - 50 wt .-% fibrous or particulate fillers or mixtures thereof
• D) 0-30% by weight of conventional additives and processing aids

for the production of moldings by blow molding, profile extrusion and / or pipe extrusion.

The invention further relates to a method for producing the polyamide molding compositions that can be used and the moldings obtainable therefrom.

Polyamides are a class of engineering materials that are used in many areas because they have an overall interesting range of properties.

A large number of applications describe polyamide molding compositions which have been specifically modified for specific applications. DE-A-26 22 973, in which a large number of possible impact modifiers for polyamide are described, is just one example.

Toughened polyamides with ethylene copolymers include known from EP-A-279 578; Molding materials containing glass fibers are known from DE-A 27 03 416, which contain ethylene or propylene homopolymers which are grafted with unsaturated acids.

However, the known tough modified polyamides can only be processed into blow molded articles to a limited extent. In blow molding, a tube of polymer melt is generally extruded, which hangs between the two half-shells of the opened tool. The tool is then closed and the polymer tube is pressed against the tool by internal gas pressure, cooled and removed from the mold.

An essential prerequisite for this processing is that the polymer tube does not tear off during extrusion in the periods where it hangs freely between the tools, so that the molding process can be completed. It is also desirable that the hose does not "sag" because this creates small wall thicknesses in the upper half and thicker wall thicknesses in the lower half. Hollow bodies with different wall thicknesses are not suitable for use because the load capacity is usually limited by the point with the smallest wall thickness. The molding compositions known from JP-A 62/252 453 and WO-A 90/7549 are therefore only of very limited suitability for the blow molding process, since the tube strength is too low.

The risk of melt breakage or sagging is particularly problematic in the case of glass fiber-reinforced polymer melts, since these have a high density (and therefore a high tensile force on the upper part of the polymer tube) and, at the same time, the maximum elasticity of the polymer melt before breaking is lower with these reinforced masses.

Both factors are determined by the so-called melt stiffness, which primarily depends on the melt viscosity. A high melt viscosity with low shear would be ideal - i.e. after extrusion - but a low melt viscosity under high shear rate - i.e. in the processing extruder.

Consequently, high molecular weight polyamides are usually used for blow molding, as is known from DE-A-38 31 243 and JP-A 60/171 133.

The assembly of high-molecular polyamides with glass fibers is not possible, however, since the molecular weight is reduced during assembly, so that - even when using high-molecular ones Starting polymers - in any case unsuitable, glass fiber-containing materials are produced for blow molding.

US Pat. No. 5,026,763 describes a granulate mixture of PA6 and glass fiber-containing PA66 with a high molecular weight for the blow molding process. The flowability of such mixtures has been improved, but the low total glass fiber content leads to limited mechanical properties. The handling of granulate mixtures usually leads to inhomogeneous moldings (segregation). Furthermore, the processing temperature must be above the melting point of the higher-melting component, which leads to lower melt viscosity of the lower-melting component and thus to poor processability of the mixture.

The present invention was therefore based on the object of providing polyamide molding compositions which can be processed in a reinforced and unreinforced manner to blow moldings, profile extrudates or tube extrudates, so that in particular moldings with a large volume can be produced from these compositions.

According to the invention, this object is achieved by using polyamide molding compositions according to claim 1.

Preferred embodiments can be found in the subclaims.

Surprisingly, it was found that the rubber, which is present in small amounts, increases the melt viscosity of the polyamide molding compositions, etc. both with reinforced and unreinforced masses. In addition, the rubber does not influence the preferred annealing process in the production of such compositions.

The polyamides that can be used are known per se. Examples for this are polyhexamethylene adipamide, Polyhexamethylenpimelinsäureamid, Polyhexamethylenkorksäureamid, polyhexamethyleneazelamide, polyhexamethylenesebacamide, polyhexamethylenedodecanediamide, Polyoctamethylenkorksäureamid, Polydodekamethylendodekandisäureamid, poly-11-aminoundecanamide and bis (4-aminocyclohexyl) -methanedodecane or by ring opening of lactams, for example polycaprolactam or polylaurolactam, products obtained . Also polyamides based on terephthalic or isophthalic acid as the acid component and / or trimethylhexamethylene diamine, bis (4-aminocyclohexyl) methane or 2,2-di (4-aminocyclohexyl) propane as the diamine component and polyamide base resins which are obtained by copolymerizing two or several of the aforementioned polymers or their components are suitable. Examples include copolycondensates made from terephthalic acid, hexamethylene diamine and caprolactam (PA 6 / 6T), and from terephthalic acid, isophthalic acid, adipic acid and hexamethylene diamine (PA 6T / 6I / 66).

Partly crystalline polyamides are preferably used, preferably PA 6, PA 66, PA 6 / 6T, PA 66 / 6T (copolycondensate of hexamethylenediamine, adipic acid, caprolactam and terephthalic acid) and PA 46.

These polyamides are prepared in a manner known per se (see, for example, Encyclopedia of Polymer Science and Engineering, Vol. 11, pp. 315 to 489, John Wiley & Sons, Inc. 1988.

The ratio of terminal acid groups to terminal amino groups can be controlled by varying the molar ratio of the starting compounds.

The viscosity number VZ of the polyamides that can be used is ≧ 250 ml / g, preferably 270-350 ml / g and in particular 290-320 ml / g. These are usually determined according to ISO 307 or DIN 53 727 on 0.5% by weight solutions in 96% by weight sulfuric acid at 25 ° C.

The proportion of polyamides in the molding compositions is 40 to 99.7, preferably 60 to 94 and in particular 65 to 89% by weight.

Mixtures of different polyamides can also be used.

The proportion of olefin polymers B) in the molding compositions is 0.3 to 3, preferably 0.5 to 2 and in particular 0.7 to 1.4% by weight.

• b₁) 40 - 99,8, vorzugsweise 60 - 99 Gew.-% mindestens eines α-Olefins mit 2 - 8 C-Atomen,
• b₂) 0,2 bis 20, vorzugsweise 1 - 10 Gew.-% einer ethylenisch ungesättigten Mono- oder Dicarbonsäure oder einem funktionellen Derivat einer solchen Säure.

These are made up of:

• b₁) 40-99.8, preferably 60-99% by weight of at least one α-olefin having 2-8 C atoms,
• b₂) 0.2 to 20, preferably 1 - 10 wt .-% of an ethylenically unsaturated mono- or dicarboxylic acid or a functional derivative of such an acid.

Suitable α-olefins b₁) are straight-chain or branched butenes, pentenes, hexenes, heptenes, octenes, ethylene and propylene being preferred.

Suitable monomers b₂) are maleic acid, fumaric acid, acrylic acid, methacrylic acid, itaconic acid or their functional (reactive) derivatives such as anhydrides or acid azides, maleic anhydride and acrylic acid being preferred.

The olefin polymers can moreover contain up to 50% by weight, preferably up to 30% by weight, of further monomers b₃).

Examples of such monomers which do not react with the polyamide under the processing conditions are acrylic acid esters with 4 to 22 carbon atoms, such as methyl acrylate, methyl methacrylate, butyl acrylate, ethylhexyl acrylate, cyclohexyl acrylate and ethyl acrylate.

Vinyl esters of acids with 1 to 20 C atoms such as vinyl acetate or vinyl propionate, vinyl ethers with 3 to 20 C atoms such as vinyl butyl ether, methacrylate and butyl acrylate being preferred.

Preferred are olefin polymers which contain no monomers b₃).

Preferred olefin polymers are ethylene copolymers with acrylic acid or polymers made from polypropylene which are grafted with acrylic acid or maleic anhydride.

The olefin polymers described above can be prepared by processes known per se, which are described in the literature.

The melt index of the olefin polymers is generally from 1 to 100 g / 10 min, preferably 5 to 25 g / 10 min (measured at 190 ° C. and 2.16 kg load).

Mixtures of the above olefin polymers can of course also be used.

As component C), the molding compositions which can be used according to the invention can contain 0 to 50, preferably 5 to 35 and in particular 10 to 25% by weight of a fibrous or particulate filler or mixtures of such fillers.

Fibrous fillers which may be mentioned here are, for example, glass fibers, carbon fibers, aramid fibers, potassium titanate fibers and fibrous silicates such as wollastonite, preferably glass fibers.

If glass fibers are used, they can be equipped with a size and an adhesion promoter, preferably an aminosilane, for better compatibility with the thermoplastic polyamide.

In general, the glass fibers used have a diameter in the range from 6 to 20 μm. The incorporation can take place both in the form of short glass fibers and in the form of endless strands (rovings). In the finished injection molded part, the average length of the glass fibers is preferably in the range from 0.08 to 5 mm.

Glass spheres, particulate wollastonite, quartz flour, boron nitride, kaolin, calcium carbonate (chalk), magnesium carbonate and titanium dioxide may be mentioned here as representative fillers, of which wollastonite, titanium dioxide and kaolin are generally preferred.

In addition to the essential components A) and B) and, if appropriate, C), the molding compositions according to the invention can contain customary additives and processing aids D). Their proportion is generally up to 30% by weight, preferably up to 10% by weight, based on the total weight of the components.

Typical additives are, for example, stabilizers and oxidation retardants, agents against heat decomposition and decomposition by ultraviolet light, lubricants and mold release agents, dyes, pigments, plasticizers and flame retardants.

Oxidation retarders and heat stabilizers which can be added to the thermoplastic compositions according to the invention are e.g. Halides selected from the group of metals of group I of the periodic table, e.g. Lithium, sodium, potassium halides, and copper (I) halides, e.g. Chlorides, bromides or iodides, or mixtures thereof. Zinc fluoride and zinc chloride can also be used. It is also possible to use sterically hindered phenols, secondary, aromatic amines, hydroquinones, substituted representatives of this group and mixtures of these compounds, preferably in a concentration of up to 1% by weight, based on the weight of the mixture.

Examples of UV stabilizers are substituted resorcinols, sterically hindered phenols, salicylates, benzotriazoles and benzophenones, which can generally be used in amounts of up to 2% by weight.

Lubricants and mold release agents which can generally be added to up to 1% by weight of the thermoplastic composition are, for example, stearic acid, stearyl alcohol, alkyl stearates and amides, and esters of pentaerythritol with long-chain fatty acids.

For example, red or black phosphorus or a phosphorus-containing compound in amounts of 3 to 10% by weight can be used as the flame retardant.

The preferred flame retardant is elemental phosphorus, in particular in combination with glass fiber-reinforced molding compositions, which can be used in untreated form.

However, preparations in which the phosphor is superficial with low molecular weight liquid substances such as silicone oil, paraffin oil or esters of phthalic acid or adipic acid or with polymeric or oligomeric compounds, e.g. are coated with phenolic resins or aminoplasts and polyurethanes.

Other preferred flame retardants are organic phosphorus compounds such as the esters of phosphoric acid, phosphorous acid and of phosphonic and phosphinic acid as well as tertiary phosphines and phosphine oxides. Triphenylphosphine oxide may be mentioned as an example. This can be used alone or mixed with hexabromobenzene or a chlorinated biphenyl and, optionally, antimony trioxide.

Compounds which contain phosphorus-nitrogen bonds, such as phosphonitrile chloride, phosphoric acid ester amides, phosphoric acid amides, phosphinic acid amides, tris (aziridinyl) phosphine oxide or tetrakis (hydroxymethyl) phosphonium chloride, are also suitable as flame retardants.

The molding compositions which can be used according to the invention can be prepared by processes known per se. The preparation is preferably carried out by adding component B) and optionally C) to the melt of component A) and optionally D), component A having a viscosity number ≦ 190, preferably ≦ 200, and in particular ≦ 225 ml / g.

For this purpose, extruders are expediently used, for example single-screw or twin-screw extruders or other conventional plasticizing devices such as Brabender mills or Banbury mills.

The plastic mixtures are then generally subjected to a further thermal treatment. In tempering units such as In a tumbler mixer or continuously or discontinuously operated tempering tubes, the molding compound present in the respective processing mold is tempered until the viscosity number of the polyamide reaches the desired VZ of ≧ 250 ml / g and above. The temperature range of the tempering depends on the melting point of the pure component A). Preferred temperature ranges are 5 to 50, preferably 20 to 30 ° C below the respective melting point of A). The process according to the invention is preferably carried out in an inert gas atmosphere, nitrogen being preferred as the inert gas.

The residence times are generally from 0.5 to 50, preferably 4 to 20 hours. Annealing presents no problems, since the olefin polymer used does not hinder the molecular weight build-up of the polyamide. Then molded parts are produced from the molding compositions by means of conventional devices for blow molding, profile extrusion and pipe extrusion.

The melt viscosity of the molding compositions is increased to such an extent that moldings, in particular those containing glass fibers, can be produced with large volumes, which have a uniform wall thickness over the entire molding. Fuel, lubricant or brake fluid containers in motor vehicles are mentioned as applications.

Examples Component A (before processing):

• A / 1: Poly-ε-caprolactam (PA 6) with a viscosity number VZ of 180 ml / g (measured according to DIN 53 727, Ultramid® B35 from BASF AG).
• A / 2: PA 6 with a VZ of 215 ml / g (Ultramid® B4 from BASF AG).
• A / 3: PA 6 with a VZ of 285 ml / g (Ultramid® B5 from BASF AG).

Component B

• B / 1: a polypropylene grafted with 6% by weight acrylic acid, MFI (190 ° C./2.16 kg) of 22 g / 10 min. (Polybond® 1009 from BP Chemicals Ltd.).
• B / 2: ethylene copolymer with 7% by weight acrylic acid; MFI (190 ° C / 2.16 kg) of 10.5 g / 10 min. (Lucalen® A3710 MX from BASF AG).

Component C:

Chopped glass fibers with a fiber length of 6 mm and 10 µm filament diameter, which were coated with an aminosilane size. (Silenka® 8044 from Silenka).

Component D)

Heat stabilizer based on CuI / KI complex.

Preparation of the mixtures

Components A) and D) were metered in a twin-screw extruder (ZSK 53) at 280 ° C (40 kg / h throughput; 120 rpm) and processed into a homogeneous melt. Glass fibers C and then component B) were optionally metered into this polymer melt, homogenized, extruded and granulated.

The granules obtained were annealed in a double-walled glass tube (flowed through with 120 1 / h N₂) of 10 cm inside diameter and 140 cm inside length at 180 ° C to the final viscosity number given in the tables, the annealing time being between 12 and 18 h.

Rectangular hollow bodies of 18.5 x 18.5 cm cross section and 61 cm in length (volume approx. 21 l, weight between 1 and 2 kg) were produced on an extrusion blow molding machine (Voith) at 275 ° C. using a discontinuous procedure.

Measurement methods:

The wall thickness is determined by measurements 10 cm below or above the bottom or lid of the hollow body. The MVI of the polyamide was determined in accordance with DIN 53 735 at a load of 10 kg and the temperatures given in the tables.

Compositions of the molding compositions

All compositions contained 100 ppm Cu in the form of a CuI / KI complex.

The results of the measurements and the composition of the molding compositions can be found in the tables.

Claims (7)

Use of thermoplastic polyamide molding compositions containing A) 40-99.7% by weight of a polyamide with a viscosity number ≧ 250 ml / g B) 0.3-3% by weight of an olefin polymer built up from b₁) 40-99.8% by weight of at least one α-olefin with 2-8 C atoms, b₂) 0.2-20% by weight of an ethylenically unsaturated mono- or dicarboxylic acid or a functional derivative of such an acid, C) 0 - 50 wt .-% fibrous or particulate fillers or mixtures thereof D) 0-30% by weight of conventional additives and processing aids for the production of moldings by blow molding, profile extrusion and / or pipe extrusion. Use of thermoplastic polyamide molding compositions according to claim 1, in which component A) has a viscosity number ≧ 260 ml / g. Use of thermoplastic polyamide molding compositions according to claims 1 and 2, in which component B) is an ethylene-acrylic acid copolymer or a polypropylene homopolymer grafted with maleic anhydride. Process for the preparation of the polyamide molding compositions which can be used according to claims 1 to 3, characterized in that component B) and, if appropriate, C) are added to the melt of component A) and, if appropriate, D), component A) having a viscosity number ≦ 190 ml / g and then these mixtures are thermally aftertreated at temperatures of 5 to 50 ° C. below the melting point of the pure component A) under inert gas conditions for a period of 0.5 to 50 hours. Blow molded articles obtainable from the polyamide molding compositions which can be used according to claims 1 to 3. Profile extrudates obtainable from the polyamide molding compositions which can be used according to claims 1 to 3. Pipe extrudates obtainable from the polyamide molding compositions which can be used according to claims 1 to 3.